(1) Field of the Invention
The present invention relates to a paper splicing device for continuously splicing a paper sheet of a preceding paper roll to a paper sheet of the succeeding paper roll, without any interruption of operation such as printing, when the rest of the preceding paper roll is rotated at a high speed in order to feed the paper sheet to, for example, a printing machine is small.
(2) Description of the Prior Art
Conventional paper splicing devices can be classified into a first device in which a paper splicing treatment is achieved while the rotation of a preceding paper roll is stopped and a second device in which a paper splicing treatment is achieved while the preceding paper roll is rotated.
In the first device in which a paper splicing treatment is achieved while the rotation of a preceding paper roll is stopped, a great deal of the paper sheet must be prepared so as to feed the paper sheet without interrupting the operation of printing or the like, even while the rotation of the preceding paper roll is stopped. Therefore, an accumulator comprising a number of dancer rollers which are movable in upward and downward directions is provided. Furthermore, in the second device in which a paper splicing treatment is achieved while the preceding paper roll is rotated, rotation driving force is applied to shaft portions of the preceding and succeeding paper rolls. However, unless a peripheral speed of the succeeding paper roll is perfectly adjusted to tune to a paper delivery speed of the preceding paper roll, excessive tensile strength is applied to the paper after the splicing operation and finally breaks the paper on occasion, or alternatively excessive sag is given to the paper, so that print non-uniformity, wrinkles and the like tend to occur in the subsequent process using a printing machine and the like. Thus, the following manner has been usually taken: In order to tune the paper delivery speed of the preceding paper roll to the peripheral speed of the succeeding paper roll, a rotational frequency and a diameter of the rotary shaft of the preceding paper roll are measured by an optical technique to seek the paper delivery speed of the preceding paper roll, and a diameter of the paper roll is previously measured to seek a rotational speed of the succeeding paper roll.
In both the cases of the first and second devices, the paper of the preceding paper roll is cut after the paper splicing operation. However, if the spliced portion of the papers is long, jamming is liable to take place, and a plate and a bracket of the printing machine are damaged at times in the subsequent printing process, which brings about more intricate jamming in a further process. For this reason, it is desirable that the spliced portion of the paper is as small and constant as possible.
In the above-mentioned first conventional device, the accumulator is necessary as described hereinbefore, and so a large-scale paper splicing device taking a very large occupational area is required inconveniently.
In addition, with regard to the above-mentioned second conventional device, it is difficult to accurately detect a peripheral speed of the paper roll and it is also hard to tune advantageously the peripheral speed of the preceding paper roll to that of the succeeding paper roll, though this device is not so oversize.
Morever, since the preceding and succeeding paper rolls are rotated during the paper splicing operation, it is difficult to precisely carry out the paper splicing operation and the cutting operation. Particularly in the case of the cutting operation, time lag arises inevitably, since an air cylinder or the like is used in a driving mechanism of a knife, with the result that the adjustment of cut timing is difficult. This difficulty has been heretofore solved by constantly maintaining the paper delivery speed during printing, or alternatively by causing the paper delivery speed in the paper splicing step to differ from the paper feed speed during the printing step, constantly maintaining the paper delivery speed, and delaying a cut command signal by the use of a timer to adjust the cut timing. However, when the paper delivery speed must often be changed in compliance with a kind of paper, the number of colors and a kind of ink, the above-mentioned manner of constantly maintaining the paper delivery speed is not suitable.